Field of the Invention
The present invention relates to an organic thin film transistor, an organic semiconductor thin film, and an organic semiconductor material. Specifically, the invention relates to an organic semiconductor material for a non-light-emitting organic semiconductor device containing a compound having a benzobisbenzofuran (which may be hereinafter referred to as BBBF) structure, an organic semiconductor thin film containing the material, and an organic thin film transistor using the thin film.
Background Art
A device using an organic semiconductor material is expected to have various advantages as compared to a device using an ordinary inorganic semiconductor material, such as silicon, and thus is receiving a high level of interest. Examples of the device using an organic semiconductor material include a photoelectric conversion device using an organic semiconductor material as a photoelectric conversion material, such as an organic thin film solar cell and a solid-state imaging device, and a non-light-emitting organic transistor. A device using an organic semiconductor material has a possibility of producing a large area device at a low temperature and low cost, as compared to a device using an inorganic semiconductor material. Furthermore, the material characteristics may be easily changed by changing the molecular structure thereof, thereby providing a wide range of varieties of the materials, and thus functions and devices that are not achieved with an inorganic semiconductor material may be realized.
For example, Patent Reference 1 describes the compound represented by the following general formula having a condensed ring containing five rings including aromatic heterocyclic rings as a partial structure (in which ring A and ring B each represent a benzene ring or a particular 5-membered aromatic heterocyclic ring; T1 and T2 each represent sulfur, selenium, tellurium, oxygen, phosphorus, boron or aluminum; R1 to R4 each represent a hydrogen atom, an alkyl group, or the like; and l and m each represent 0 or 1). Patent Reference 1 describes that the compound represented by the following general formula may form a semiconductor active layer and may be an organic semiconductor material that is capable of forming the film by coating. In the literature, the compound is used as an organic semiconductor material and forms an organic thin film, but the transistor characteristics and the like thereof are not described.

Patent Reference 2 describes an example of the application as an organic EL device of a condensed ring compound containing an aromatic heterocyclic ring that is defined in structural characteristics from the other view point than the aforementioned general formula. However, Patent Reference 2 fails to describe examples of an application as an organic transistor and transistor characteristics.
Non-patent Reference 1 and Patent References 3 to 6 describe the use of a polycyclic condensed ring compound containing an aromatic heterocyclic ring as an organic transistor. Non-patent Reference 1 suggests that some of compounds having a BBBF skeleton appear promising as a material for an organic thin film transistor. However, the organic thin film transistor only has transistor characteristics that are in an elementary level and fails to achieve a practical level due to the low mobility. Patent References 3 to 6 describe the usefulness of a compound having a BBBF skeleton in an organic semiconductor device, but only the limited compounds are shown to have the usefulness as an organic semiconductor material for an organic thin film transistor.